Fosi Audio TB10D TPA3255, Is That An Amp In Your Pocket?

A Pocket Sized Stereo Amplifier

A Product In Search Of An Application?

This is the first time we have taken a look at a Fosi Audio product at PCPer; not even a link to someone’s review on another site.  They are a Chinese company which somewhat recently expanded their business overseas.  They specialize in “Hi-Fi products, DIY kits and DIY guidance for audiophiles“.  Their products include amps and pre-amps for passive speakers or headsets, DACs, Bluetooth receivers, and even some DIY kits, all at a non-audiophile price point.

What we have here is the TB10D TPA3255, a stereo power amplifier with basic treble, bass and volume controls.  While it is barely the size of a paperback book it is has two analog channels each of which are capable of driving up to 315 W into a 4-Ω load at 10% total harmonic distortion or two 150 W unclipped into an 8-Ω load.   It is up against a venerable Kenwood KR-V87R stereo tuner/amp, and will be attached to five pairs of 8-Ω speakers sporting a variety of maximum wattages, all over 100W.

Good Things Come In Small Packages

A tiny stereo amplifier designed to be connected to unpowered speakers seems an odd thing, as you aren’t often called upon to produce an amp while you are out and about, except perhaps a headphone amp which the Fosi Audio TB10D TPA3255 is not.  Then again, there is an attractiveness to having a portable 600W amp, or one that takes up a minuscule amount of space on a shelf.  Considering the variety of products Fosi Audio sells there must be something to this.

The $75 cost to purchase it is certainly in it’s favour, much less expensive than some more traditional stereo amps, especially those with more than just two channels.  The specifications are another interesting feature, this Class-D amplifier is powered by a Texas Instruments TPA3255 chipset that provides a PurePath Ultra-HD signal with very low distortion.   It is hard to complain about a frequency range of 20Hz – 40kHz nor a signal to noise ratio of 90dB.  It is also kind of cute in an industrial sort of way though the phono pre-amp with vacuum tubes beats the TB10D TPA3255 in that department.

A Very Pleasant Surprise

The poor ancient Kenwood, which is over 30 years old, has been powering a variety of my speakers for several decades.  Over that time it has developed some grounding issues and the higher end intermittently becomes quite muffled making movie dialog a little hard to hear.  As percussive maintenance and a quick flick to the equalizer resolves these problems, it has stuck around as it is still just good enough.  There is also the fact that many modern amps do not have posts for bare wires, so an upgrade would likely involve new speakers as well as an amp.   It also sports front and rear channels in addition to left and right, as well as one of the first incarnations of Dolby Surround, neither of which is provided by the Fosi TB10D TPA3255.

After a bit of work, the wire transplant was successful and the TB10D TPA3255 is ready to try powering an obnoxious amount of speakers.  A flick of the power button and suddenly the room is filled with clearer and louder sound than it has been since I last pulled my NAD amp out for testing.  The signal is just stereo, with no front nor rear channels but there was no question those channels were perfectly separated and fully audible all around the room.

The audio is not delayed at all compared to the source, though it certainly does overwhelm it.  The amp offers very clean voice performance for watching TV, and there is no question the treble and bass switches do exactly as much as you’d expect.  When swapping over to movies, the separation continues with the effects being just as loud as you like while not fuzzing out dialogue.  The amp really shines when you fire up your favourite music, with very clear audio.  Those that prefer a warm tone might not favour the TB10D TPA3255, as it doesn’t have quite the same warmth as the old Kenwood.  The lack of Dolby Surround is telling, but that would not matter at all if these were used in a more normal fashion and hooked up to a pair of high end bookshelf speakers.

Titillating

By their very nature audio reviews are qualitative and not quantitative, so your ears may not agree with mine.  In this case I was able to garner a second opinion from a musician friend who has so far refused to try out the Monoprice headphones as they don’t cost $500 and so won’t be anywhere near the quality of his Sennheiser headphones.   His first comment was to congratulate me on making the Kenwood sound acceptable again.  When I explained that we were listening to the Fosi Audio TB10D TPA3255 which we both originally questioned the usage of; “titillating” was his response.

If his monitors weren’t powered, something like this would make a lot of sense.  Clean sound and a tiny footprint on the desk are both valuable attributes.  If you have a nice pair of bookshelf speakers, or another setup which just wants a stereo signal then for the price this amp is a great solution.  You probably shouldn’t use it the way I have, but it can certainly handle it with no noise or distortion though upgrading to a 48V/10A power supply is recommended to get the best experience .  The build quality is such that you can take it on the road without worry as well, for after all it is billed as a pocket amp.